<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        /*body总有一个外边距,常见操作
        h1,ul,li,a,body{
            margin: 0;
            padding: 0;
            text-decoration: none;
        }*/
        /* border:粗细 样式 颜色 */
        #box{
            width: 300px;
            border: 1px solid red;
        }
        form{
            background: #1ec659;
        }
        div:nth-of-type(1) input{
            border: 3px solid black;
        }
        div:nth-of-type(2) input{
            border: 3px dashed green;
        }
        div:nth-of-type(3) input{
            border: 2px solid #7131a6;
        }
        h2{
            font-size: 16px;
            background: #1ec659;
            line-height: 30px;
            color: white;
        }
    </style>
</head>
<body>
<div id="box">
    <h2>会员登录</h2>
<form action="#" >
    <div>
        <span>用户名:</span>
        <input type="text">
    </div>
    <div>
        <span>密码:</span>
        <input type="text">
    </div>
    <div>
        <span>邮箱:</span>
        <input type="text">
    </div>
</form>
</div>
</body>
</html>